The present invention relates to a resist process method and system for coating a substrate such as a semiconductor wafer with a resist solution, and developing the resist coating.
In a photolithographic process, a resist process system is used to sequentially coat semiconductor wafers with a resist solution, and develop the resist coatings. Such resist process systems are disclosed in U.S. patent Ser. Nos. 08/667,712 and 08/686,707. In these resist process systems, wafers are conveyed to the respective process units by using a plurality of arm mechanisms to be sequentially processed. When a series of processes are complete, the wafers are stored in a cassette in a cassette station, and are conveyed outside the system together with the cassette.
During these processes and conveyance, various types of foreign substances may adhere to wafers. Foreign substances, e.g., a developing solution, particles, various types of organic substances, and various types of ions are likely to adhere to the rear surfaces of wafers, in particular. U.S. patent Ser. No. 08/521,845 discloses an apparatus and method which prevent contamination of the rear surfaces of wafers during a developing process. This conventional technique is designed to only prevent contamination of the rear surface of a wafer during a developing process, but cannot remove foreign substances adhering to the rear surface of the wafer after the developing process. If, for example, a resist solution or developing solution adheres to the holder of an arm mechanism for some reason, these substances are transferred to the rear surface of a wafer, and the contaminated wafer is stored in a cassette as it is. In addition, particles floating in the system may adhere to the processed wafer, and the contaminated wafer may be stored in a cassette as it is.
The resist process system also uses chemical filters to remove organic components from the atmosphere in the system. A chemical filter is expensive and demands frequent replacement of elements. For this reason, in a resist process system, the quantity of chemical filters used is preferably minimized. In the conventional resist process system, however, since chemical filters are provided for a brush cleaning device and a water cleaning device which are irrelevant to organic components, the quantity of chemical filters used in the system is large as a whole.